Thermal shock resistance of thermal barrier coatings modified by selective laser remelting and alloying techniques

Abstract Aiming to improve the thermal shock resistance of thermal barrier coatings (TBCs), the plasma‐sprayed 7YSZ TBCs were modified by selective laser remelting and selective laser alloying, respectively, in this study. A self‐healing agent TiAl 3 was introduced into the 7YSZ TBCs by selective laser alloying to fill cracks during thermal cycling. The thermal shock experiments of the plasma‐sprayed, laser‐remelted, and laser‐alloyed TBCs were conducted by a means of heating and water‐quenching method. Results revealed that some segmented microcracks were distributed on the surface of the laser‐remelted and the laser‐alloyed zones, showing a dense columnar crystal structure. After thermal shock tests, the numbers of segmented microcracks on the laser‐remelted coating increased, whereas, in the laser‐alloyed condition, some irregular particles formed, leading to the decreased numbers of segmented microcracks. The laser‐alloyed coating exhibited the best thermal shock resistance, followed by the laser‐remelted condition, with the thermal shock lifetime 3.3 and 2.7 times higher than that of the as‐sprayed coating, respectively. On the one hand, both columnar grains and segmented microcracks in the laser‐treated zone could effectively improve the strain tolerance of coatings. On the other hand, the oxidation products of TiAl 3 under high‐temperature condition could seal the microcracks to postpone the crack connection. Thus, the thermal shock resistance of the laser‐treated coatings was significantly improved.